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Electronic Controls
The 3176B electronic system consists of two components, the Electronic Control Module (ECM) and the Personality Module, and various sensors. The ECM is the computer which controls the 3176B engine. The Personality Module contains the software which controls how the ECM behaves (stores the operating maps that define power, torque curves, rpm, etc). Early machines have a separate Personality Module component. Later machines have the Personality Module integral to the ECM. For information, refer to Programming Parameters section in this manual.The ECM determines a "desired rpm" based on the throttle input signal and certain diagnostic codes. The ECM then maintains the desired engine rpm by sensing actual engine rpm and deciding how much fuel to inject in order to achieve the desired rpm.Fuel Injection
The ECM controls the amount of fuel injected by varying signals to the injectors. The injectors will inject fuel ONLY if the injector solenoid is energized. The ECM sends a high voltage signal to the solenoid to energize it. By controlling the timing and duration of the high voltage signal, the ECM can control injection timing and the amount of fuel injected.The ECM sets certain limits on the amount of fuel that can be injected. "FRC Fuel Pos" is a limit based on boost pressure to control the fuel-air ratio, for emissions control purposes. When the ECM senses a higher boost pressure (more air into cylinder), it increases the "FRC Fuel Pos" limit (allows more fuel into cylinder). "Rated Fuel Pos" is a limit based on the horsepower rating of the engine. It is similar to the rack stops and torque spring on a mechanically governed engine. It provides horsepower and torque curves for a specific engine family and rating. All of these limits are programmed at the factory into the Personality Module and are not programmable in the field.Injection timing depends on engine rpm, load and other operating factors. The ECM knows where top-center on cylinder number one is from the signal provided by the engine Speed/Timing Sensor. It decides when injection should occur relative to top-center and provides the signal to the injector at the desired time.Fuel Temperature Monitoring
The Fuel Temperature Sensor monitors the fuel temperature and adjusts the ECM calculated fuel rate to compensate for fuel temperature changes.For fuel temperatures above 30°C (86°F) the ECM will adjust the rated fuel position to provide constant power.Altitude Derate
This feature protects the engine at altitudes above 2286 meters (7500 feet) by using the atmospheric pressure sensor input (less than 67 kPa [9.7 psi]) to the ECM. The ECM will adjust engine operating parameters to reduce engine rpm and power.Lifetime Operating Data Totals Stored In The ECM
The ECM maintains engine total data for the following parameters. These parameters are available using an Electronic Service Tool. Engine Hours is engine running hours. It does not include time when the ECM is powered ON, but the engine is not running (engine OFF). Fuel Used is the fuel consumption value determined by the ECM.Passwords
"System Configuration Parameters" are protected by Factory Passwords. Factory passwords are calculated on a computer system available only to Caterpillar dealers. Since factory passwords contain alphabetic characters, only the Electronic Service Tool may change System Configuration Parameters. System Configuration Parameters affect the power family or emissions."Customer Parameters" are protected by Customer Passwords. The customer passwords are programmed by the customer.Refer to Programming Parameters for more details when passwords are needed and how to obtain them.Self-Diagnostics
The 3176B electronic system has some ability to diagnose itself. When a problem is detected, a diagnostic code is generated and the Diagnostic/Check Engine Lamp is ON. In most cases, the code is also stored in permanent memory in the ECM.Codes stored in memory are called LOGGED. Since the problem may have been temporary or may have been repaired since the time it was logged, logged codes do not necessarily mean something needs to be repaired. They are instead meant to be an indicator of probable causes for intermittent problems. In addition, some logged codes record "events", rather than failures. Codes not requiring passwords to clear are automatically deleted after 100 ECM hours. See the section on "Troubleshooting With A Diagnostic Code" in this manual for more details.3176B EUI Electronic System Diagram 3176B Component Diagram 3176B Sensor and Connector Locations Electrical Connectors and Functions
Inspecting Electrical Connectors
Many of the Functional Tests in this troubleshooting guide will direct you to check a specific electrical connector. If a problem is found in the electrical connector, repair the connector and continue the test procedure. Check to make sure all seals are present, and properly seated, check pins and sockets for evidence of corrosion before joining connectors. The connector seals must be present. If corrosion is evident on pins, sockets or the connector itself, use only denatured alcohol to clear/remove the corrosion with a cotton swab. Check DT connector locking, and HD connector lock ring. Make sure that the connector is properly locked (clicked) together and that the two halves cannot be pulled apart. Do not exceed 2.25 N m (20 lb in) of torque on the ECM Connector Bolt (Allen head) when connecting the 40-Pin DRC connector to the ECM. Perform pull test on each pin/wire. Each pin and connector should easily withstand 45 N (10 pounds) of pull, and remain in the connector body. DT connectors use an orange wedge to lock the pins in place. Check to see that the orange wedge is not missing and installed properly on the DT connectors. Pins should ALWAYS be crimped onto the wires using a Deutsch Crimp Tool; NEVER soldered. Use the 1U5804 Deutsch Crimp Tool. Check individual pin and socket connections. This is especially important for intermittent problems.Electronic Service Tools
The Caterpillar Electronic Service Tool is designed to assist the service technician for analyzing and locating problems, diagnostics and component failures within the system. It is required to perform some sensor calibrations electronically, and to read or change programmable engine parameters. The basic tool has small plug-in modules, called Service Program Modules (SPM), to adapt